1. Field of the Invention
The present invention relates to an image quality adjustment method, image forming apparatus and a computer readable medium for adjusting quality of image that is to be recorded on a recording sheet.
2. Description of Related Art
An image forming apparatus with an electrographic manner, such as a copying machine, printer and a facsimile, performs an image recording job: such as to expose a photoconductor drum; form an electrostatic latent image by the exposure; develop the formed electrostatic latent image with toners to form a toner image; record the formed toner image on a recording sheet and to export the recording sheet.
The image forming apparatus includes a development apparatus that is roughly classified into two types: a development apparatus with monocomponent development method that utilizes single component toners; and a development apparatus with two component development method that utilizes two component developers including non-magnetic toners and magnetic carriers. Although the monocomponent development manner is suitable for downsizing the image forming apparatus, it is not suitable for implementing fast development and has a problem such as a limited toner life. Thus, the two component development method is generally utilized for the image forming apparatus.
When a development apparatus with the two component development method carries out a development process, non-magnetic toners are consumed while magnetic carriers are not consumed. Thus, an amount of the non-magnetic toners is reduced inside the development apparatus, while the magnetic carriers remain inside the development apparatus. A reduction of a toner amount causes deteriorating image quality. For keeping image quality of the development apparatus with the two component development manner, non-magnetic toners should be additionally supplied at proper timing, to keep a constant toner density of the two component developers
Furthermore, image quality of image forming apparatus is affected by deterioration of a photoconductor drum and two component developers, changing environmental conditions such as temperature and moisture, and the like. Thus, a general image forming apparatus automatically adjust image quality again, when a number of recording sheets having recorded image becomes no less than a predetermined number after image quality has been adjusted once, for keeping constant image quality.
However, an image recording job is not carried out during adjusting image quality. Thus, a user may happen to wait until the image quality adjustment is completed. Therefore, it is important to recognize a proper start timing of an image quality adjustment, for keeping up both convenience for a user and stability of image quality.
Recently, several image quality adjustment techniques are disclosed (process control technique), and process controls are carried out in accordance with detailed image forming conditions.
For example, an image forming apparatus is disclosed to adjust a timing of a process control, in accordance with a formed image ratio of monochrome image and color image (Japanese Patent Application Laid-Open No. 2003-91224). A monochrome image generally does not require higher image quality than a color image. Thus, in the case of a higher monochrome image ratio, the image forming apparatus shown in Japanese Patent Application Laid-Open No. 2003-91224 does not carry out a process control even when the number of recording sheets each having a recorded image becomes no less than a predetermined number. Then, this allows shortening a period of time when an image recording job cannot be carried out, because a wasteful process control is not carried out. Thus, it is possible to keep up both convenience for a user and stability of image quality.
Furthermore, an image forming apparatus is disclosed which carries out a process control when a predetermined period of time has passed since an image recording job is completed (Japanese Patent Application Laid-Open No. 2006-220959). For example, a user generally does not use the image forming apparatus at lunch break or after office hours, and it is assumed to have much time from a completion of an image recording job to a start of the next image recording job during such time periods. Thus, a process control is carried out during these time periods, for keeping up both convenience for a user and stability of image quality.